Insight
Classic fifth-edition (2014) SRD 5.1 rules. The complete rules for this entry are reproduced below for use at the table.
Ability: WIS
Your Wisdom (Insight) check decides whether you can determine the true intentions of a creature, such as when searching out a lie or predicting someone's next move. Doing so involves gleaning clues from body language, speech habits, and changes in mannerisms.